Valid Palindrome
描述
Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.
For example,
"A man, a plan, a canal: Panama" is a palindrome.
"race a car" is not a palindrome.
Note: Have you consider that the string might be empty? This is a good question to ask during an interview.
For the purpose of this problem, we define empty string as valid palindrome.
分析
无
代码
// Valid Palindrome
// 时间复杂度O(n)，空间复杂度O(1)
class Solution {
public boolean isPalindrome(String s) {
s = s.toLowerCase();
int left = 0;
int right = s.length() - 1;
while (left < right) {
if (!Character.isLetterOrDigit(s.charAt(left))) ++left;
else if (!Character.isLetterOrDigit(s.charAt(right))) --right;
else if (s.charAt(left) != s.charAt(right)) return false;
else { ++left; --right; }
}
return true;
}
}